1. Field of the Invention
The present invention falls within the field of water sports the practitioner of which uses a pulling force for his displacements, such as the muscle energy of a human being or the wind energy, or a vehicle or an engine, namely the so-called “sliding” sports, in particular using a watercraft or traction sail, preferably kitesurfing.
The present invention will find a preferred, but in no way restrictive, application for kite surfing, but may be suitable for wakeboarding, windsurfing and surfing, or even kayaking.
The invention specifically relates to a foil device intended to be fastened to and to extend under the lower side of a watercraft or a board for practicing such water sports.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
In a known way, a foil is derived from the Anglo-Saxon term “hydrofoil”, hereinafter referred to as “foil”. A foil is a wing that moves in and into contact with the water, the hydrodynamic profile of which transmits to its support a lift force orthogonal to the direction of displacement of the board.
Such a foil is typically provided with at least one pole extending vertically, fixed in a removable way at the level of its upper extremity to the lower side of the board and connected at the level of its lower extremity to a wing. The latter extends laterally, generally symmetrically on both sides of a fuselage, with respect to the plane of the pole, aligned with the longitudinal median plane of the board. The wing can be formed by a single element, but it is generally comprised of at least two separate portions, a front one and rear one, permitting to obtain lever arms and moments necessary for the longitudinal stability for pitching and side stability for rolling.
Most existing foils are formed either of a single block forming the pole and the fuselage, the wings being removable or a pole and a block constituting the fuselage and wings, the block is removable. Though this single-block embodiment provides this foil with a high mechanical strength, it raises a problem for its transportation and its storage. This single-block foil has bulky dimensions, making its transportation as well as its assembling and disassembling for securing to the board constraining and tiresome.
It has been devised to separate the different elements forming a foil, i.e. the pole, the fuselage and wing portions, and to fasten them in a removable way to each other. Thus, once they have been disassembled, the various elements have a smaller size, which facilitates their storage and their transportation.
However, a problem lies in the removable fastening of the elements to each other and the orientation of the implemented fastening means. Indeed, the front and rear portions of the wing are applied against the pole, at the level of the fuselage, reciprocally at the front and the rear of the latter, which then has with its fuselage an inverted T-shape in the median plane of the foil, i.e. the vertical plane. This fastening occurs by screwing, transversely with respect to the plane of each wing portion, from the top or the bottom of each portion. The fastening axis is then located in a vertical plane oriented orthogonally with respect to the direction of displacement of the foil and substantially according to the lifting forces applied by each portion of the foil being moved. As a result, these constraints are applied at the level of each screw, mechanically deforming this particular point of junction. These constraints lead to a deterioration of this fastening over time, which can cause their breakage and the tearing of the wing portions.
Furthermore, in the case of several screws, the operations of assembling and disassembling the wing portions of such a foil remain tiresome and must be carried out methodically and carefully, especially as regards the assembling, in order to ensure a good fastening and a good positioning of the elements with respect to each other, providing the desired hydrodynamic characteristics.
An example of such a foil is described through US 2005/0255764. As mentioned above, such a foil comprises a pole at the lower extremity of which extends a fuselage, the unit having an inverted T-shape. A front fuselage of the fuselage receives a front wing portion fastened by screwing from above, while a rear fuselage receives a rear wing portion fastened by screwing from below.
An existing solution consists of a dismountable foil including a pole to which is fastened a fuselage that comprises removable front and rear wings. The fuselage includes two extremities, in the form of a front and rear half-cylinder complementary of a front half-cylinder comprising a front wing portion and a rear half-cylinder comprising a rear wing portion, respectively. The fuselage also includes a rod ensuring a longitudinal locking of the fuselage with the front and rear wing portions by passing through each of these parts. The rod comprises at each of its front and rear extremities a nose of the fuselage. Thus, the rear nose of the fuselage is rigidly fastened to the rod and the front nose comprises a complementary inner threading of the front extremity of the rod including in turn an outer threading. As a result, the centering and clamping of the wings to the fuselage are performed in a single step, when locking the front nose of the fuselage cooperating with the threaded extremity of the rod. In addition, the semi-cylindrical assembling of the fuselage and front and rear wing portions raises problems of putting into production. Indeed, in order to achieve an optimal centering and blocking of the semi-cylindrical parts it is necessary to manually polish each complementary part, which represents an additional production cost and time. Furthermore, the assembling of such a foil has a mechanical weakness at the level of the holding of the different parts it is comprised of (fuselage, front and rear noses of the fuselage and the front and rear wing portion), namely in view of the side or vertical forces with respect to the vector of displacement of the foil. Indeed, the rod ensures a longitudinal locking of the parts of the foil, but is also the only force holding the foil assembled against the multidirectional stresses exerted by the water onto the foil depending on its displacement. Moreover, since the fuselage is fastened to the pole over almost its entire length (except for the front and rear noses) has the disadvantage, once it has been disassembled, of having a bulky T-shaped part raising problems of storage and transportation.